Year Observations     Objects
1950            2          1 
1951            6          3 
1953            4          2 
1954            2          1 
1955            4          2 
1956            2          1 
1960            6          3 
1974            2          1 
1975            2          1 
1976            8          4 
1977            2          1 
1978            8          3 
1981            4          2 
1982           12          6 
1983            8          4 
1984            2          1 
1985            8          4 
1986            4          2 
1987            2          1 
1988           38         18 
1990           32         14 
1991          512        193 
1992          936        367 
1993         1669        610 
1994         2329        840 
1995         4410       1522 
1996         3593       1262 
1997         2334        796 
1998        23319       9830 
1999        14588       5596 
2000        40643      16874 
2001        41657      16247 
2002        32787      14652 
2003        61720      25581 
2004        48493      18605 
2005        86594      26601 
2006       112093      35786 
2007       206713      63308 
2008       127597      36275 
2009       103867      29168 
2010       120553      33451 
2011       181508      50184 
2012       168549      46630 
2013       262214      74360 
2014       652785     166441 
2015       759522     201442 
2016       579037     154467 
2017       609048     162778 
2018       407113     114102 
2019       931183     227038 
2020       702362     180386 
2021       911648     218835 
2022       681522     194929 
2023       618212     177922 
2024       138294      39631